Four-dimensional helical tomographic scanner

Abstract

A computed tomography imaging scanner (10) acquires helical cone beam projection data for a volume of interest (46) using at least two source trajectory helices. A reconstruction processor (62) reconstructs the projection data for each helix to generate a corresponding time skewed image representation. A voxel time processor (66) computes an acquisition time for each voxel in each time skewed image representation. A voxel interpolator (68) computes an interpolated voxel value for each voxel based on values of the voxel in the time skewed image representations and corresponding voxel acquisition times. In an electronic embodiment, the computed tomography scanner (10) includes an x-ray source (12) with an axially oriented cylindrical anode (92), an electron source (961, 962) irradiating the cylindrical anode (92) to produce an x-ray beam (120, 122, 124, 126), and an electron beam deflector (98, 100) that deflects the electron beam along the anode (92) to axially sweep the x-ray beam.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to the medical imaging arts. It particularly relates to high-speed and time-dependent helical or multi-slice volumetric cardiac computed tomography (CT) imaging, and will be described with particular reference thereto. However, the invention will also find application in volumetric computed tomographic imaging of other dynamically moving organs, in high resolution contrast agent intake and blood perfusion studies, and the like.[0002]Cardiac computed tomography imaging typically employs an x-ray source that generates a fan-beam, wedge-beam, cone-beam or otherwise-shaped beam of x-rays that traverse an examination region within which a patient's heart is disposed. The cardiac tissue, coronary arteries, and blood interacts with and absorbs a portion of the traversing x-rays. Typically, a contrast agent is administered to the patient to improve blood contrast. A one- or two-dimensional radiation detector arranged opposite th...

AI Technical Summary

Benefits of technology

[0015]One advantage of the present invention resides in increased reconstruction accuracy compared with conventional cardiac gating employing circular or low-pitch spiral orbits. The improved accuracy is particularly apparent for large volumes of interest.

Problems solved by technology

In cardiac imaging, problems arise due to a limited temporal resolution of computed tomography, which is controlled by the rotation rate of the x-ray source.

However, data combined from adjacent cardiac cycles may not readily form a complete data set due to angular redundancies.

Another source of error with cardiac gating is inaccuracy in associating the electrocardiographic data with the cardiac cycle.

Particularly in cases of heart arrhythmia where the cardiac cycle period is sometimes variable over a few neighboring heart beats, simple linear scaling of cardiac cycle features with cardiac cycle period is of limited accuracy.

Yet another problem with cardiac gating is that for large volume fields of view the low-pitch spiral takes a substantial length of time to span the volume of interest.

This can produce artifacts due to subject motion that vary in an unknown manner along the axial direction.

However, this increases system cost, and image artifacts can occur due to spatial non-uniformity of the large-area beam or detector.

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